1. Field of the Invention
The present invention broadly relates to self-supporting ceramic bodies and methods of making same, including composite ceramic bodies, having therein one or more channels which inversely replicate the geometry of a configured fugitive metal.
2. Background and Commonly Owned Patent Applications
The subject matter of this application is related to that of Commonly Owned U.S. Pat. No. 4,713,360, which issued on Dec. 15, 1987, and copending U.S. patent applications Ser. No. 818,943, filed Jan. 15, 1986 as a continuation-in-part of Ser. No. 776,964, filed Sept. 17, 1985 as a continuation-in-part of Ser. No. 705,787, filed Feb. 26, 1985, a continuation-in-part of Ser. No. 591,392, filed Mar. 16, 1984, all in the names of Marc S. Newkirk et al and entitled "Novel Ceramic Materials and Methods of Making The Same." This patent generically discloses the discovery of a method of making self-supporting ceramic bodies by use of a particular oxidation phenomenon to oxidize a parent metal precursor. The oxidation reaction may be enhanced by the use of a dopant alloyed into the parent metal, and affords self-supporting ceramic bodies of desired size grown as the oxidation reaction product of the parent metal.
The foregoing oxidation method was improved upon by the use of external dopants applied to the surface of the parent metal precursor as disclosed in Commonly Owned and copending U.S. applications Ser. No. 220,935, filed Jun. 23, 1988, which issued on Aug. 1, 1989, as U.S. Pat. No. 4,853,352, which is a continuation of Ser. No. 822,999, filed Jan. 27, 1986, as a continuation-in-part of Ser. No. 776,965, filed Sept. 17, 1985, as a continuation-in-part of Ser. No. 747,788, filed Jun. 25, 1985, as a continuation-in-part of Ser. No. 632,636, filed Jul. 20, 1984, all in the names of Marc S. Newkirk et al and entitled "Methods of Making Self-Supporting Ceramic Materials".
Use of the foregoing oxidation methods to make self-supporting ceramic bodies embedding one or more fillers is disclosed in Commonly Owned and copending U.S. patent application Ser. No. 819,397, filed Jan. 17, 1986 which issued on Jul. 25, 1989, as U.S. Pat. No. 4,851,375, and entitled "Composite Ceramic Articles And Methods Of Making The Same", which is a continuation-in-part of Ser. No. 647,876 filed Feb. 4, 1985, and entitled "Composite Ceramic Articles And Methods Of Making Same", both applications being filed in the names of Marc S. Newkirk et al. These copending applications disclose a novel method for producing a self-supporting ceramic composite body by growing an oxidation reaction product from a parent metal into a permeable mass of filler. The resulting composite, however, has no defined or predetermined configuration.
The ability to provide a defined or predetermined configuration to the ceramic body, i.e., the ability to grow a ceramic body to a predetermined size and shape was attained by infiltrating with the oxidation reaction product a shaped preform filler, i.e., infiltrating the shaped preform filler to its surface boundary. This technique is disclosed in Commonly Owned and copending U.S. patent application Ser. No. 861,025, filed May 8, 1986 in the names of Marc S. Newkirk et al and entitled "Shaped Ceramic Composites and Methods of Making the Same".
A further development of the foregoing methods enables the formation of self-supporting ceramic structures which contain therein one or more cavities which inversely replicate the geometry of a positive mold of shaped precursor parent metal embedded within a bed of conformable filler which is at least partially self-bonding under specified conditions as described in Commonly Owned and copending U.S. patent application Ser. No. 823,542 filed Jan. 27, 1986 which issued on May 9, 1989, as U.S. Pat. No. 4,851,375, in the names of Marc S. Newkirk et al, entitled "Inverse Shape Replication Method of Making Ceramic Composite Articles and Articles Obtained Thereby". Still another development of the foregoing methods enables the formation of self-supporting ceramic bodies having a negative pattern which inversely replicates the positive pattern of a parent metal precursor emplaced against a mass of filler, as described in Commonly Owned and copending U.S. patent application Ser. No. 896,157, filed Aug. 13, 1986 which issued on Aug. 22, 1989, as U.S. Pat. No. 4,859,640 in the names of Marc S. Newkirk and entitled "Method of Making Ceramic Composite Articles With Shape Replicated Surfaces and Articles Obtained Thereby". In both of these copending applications, the cavity inversely replicates the geometry of the parent metal.
The entire disclosures of all of the foregoing Commonly Owned and copending patent applications are expressly incorporated herein by reference. For certain applications, there is an interest in substituting ceramics for metals because, with respect to certain properties, ceramics are superior to metals. There are, however, several known limitations or difficulties in making this substitution such as scaling versatility, capability to produce complex shapes, satisfying the properties required for the end use application, and costs. The inventions set forth in the above-described Commonly Owned patent applications overcome many of these limitations or difficulties and provide novel methods for reliably producing ceramic materials, including composites.
The invention described in Commonly Owned patent application Ser. No. 823,542 (identified above) ameliorates the difficulties in formation of ceramic bodies having shapes with complicated internal cavities and especially shapes with re-entrant cavities. Conventional or known methods for making ceramic products with such shapes by compacting and sintering powder particles are not applicable, because the internal pattern required to establish the desired part geometry cannot be easily removed after the body is formed around it. While such part geometries can sometimes be prepared by machining the desired shape from a finished ceramic blank, this approach is rarely used because of the prohibitive costs.